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Abstract:

We report on a search for the flavor-changing neutral current decay D ⁰→µ⁺µ^- in pp^- collisions at √s = 1.96 TeV using 65 pb^-1 of data collected by the CDF II experiment at the Fermilab Tevatron Collider. A displaced-track trigger selects long-lived D⁰ candidates in the D⁰→µ ⁺µ^- search channel, the kinematically similar D ⁰→П⁺p^- channel used for normalization, the Cabibbo-favored D⁰K^-П^- channel used to optimize the selection criteria in an unbiased manner, and their charge conjugates. Finding no signal events in the D⁰→µ⁺µ^- search window, we set an upper limit on the branching fraction B(D⁰→µ⁺µ^-)≤2.5×10^-6 (3.3×10^-6) at the 90% (95%) confidence level.

Abstract:

We present the results of deep VLT-ISAAC Ks-band imaging of four z∼1.5 flat-spectrum quasars selected from the Parkes half-Jansky flat spectrum sample. We find that the hosts of these flat-spectrum quasars are consistent with lying on the K-z Hubble relation for radio galaxies. This implies that the flat-spectrum quasar hosts fall in line with the expectations from orientation based unified schemes and also that they contain black holes of similar mass. Moreover, the width of the Hβ broad emission line in these objects tends to be narrower than in their misaligned (low-frequency selected quasar) counterparts, implying that the width of the Hβ broad emission line depends on source inclination, at least for radio-loud quasars, in line with previous studies. © 2003 Elsevier B.V. All rights reserved.